Alloys



Patented Aug. 25, 1936 PATENT OFFICE I ALLOYS Richard A. Wilkins, Rome, N. 1., assignor to Revere Copper and Brass Incorporated, Rome, N. Y., a corporation of Maryland No Drawing.

satisfactory hardness and freely machinable,-

have long been desired.

It has been found that silicon may be added to copper or brass to increase its tensile strength,

l5 tin to increase its corrosion resistance, and lead,

tellurium and selenium to increase its machinability. Silicon however tends objectionably to decrease the machinability, ductility and cold workability of the alloy, while tin tends objectionably to decrease its hot workability, as does likewise lead, the latter also tending objectionably to decrease the hardness, thus making the addition of a combination of these three metals impractical in respect to producing a copper- 25 base alloy having the above mentioned desirable properties. Tellurium'and selenium, like silicon, have an objectionable tendency to decrease the cold workability of the alloy, and further tend seriously to affect the tensile strength, yield point, 30 ductility and hardness, making it ordinarily impracticalto add tellurium or selenium to copper or brasses containing enough silicon and tin to secure the desired high tensile strength, yield point, hardness and corrosion resistance. 35 Applicant has found however, that by properly coordinating the amounts of silicon, tin and tellurium or selenium added to copper, the desired effects will be produced in respect to securing an alloy having a high tensile strength, cor- 40 rosion resistance and ductility, both hot and cold workability, and satisfactory hardness and machinability, in spite of the fact' that one or the other of these three metals in each instance tends ,to destroy one or the other of these properties. At 45 the same time the alloy has the unique property of being capable of heat treatment at temperatures below recrystallization temperatures when in the cold drawn condition markedly to increase the yield point of the alloy without substantial 50 reduction in the tensile strength, elongation and.

hardness. I

For best results the alloys should contain from about 2.25 to 3.5% silicon. With lesser amounts of silicon the alloys are deficient in tensile 65 strength, and with higher amounts are unsatis- Application October 12 1935, Serial No. 44,763

4 Claims. (Cl. 75-154) factory in respect to cold rolling and drawing operations.

The tin, to secure best results, should be varied with the amount of silicon employed. Throughout the entire range of silicon'above, specified 5 satisfactory results will be secured with as little as about 0.25% tin. The maximum amount of tin for values of silicon between 2.25 and 3% should'not exceed a value which varies approximately from 1.8 to 2% roughly linearly and directly with the amount of silicon. The maximum amount of tin for values of silicon between 3 and 3.5% should not exceed a value which varies approximately from 1.7 to 2% roughly linearly and inversely with the amount of silicon. Values of tin materially in excess of those indicated as the maximum permissible amount ordinarily will make the alloy unsatisfactory in respect to hot workability. Best results in respect to the peak values of the characteristic properties of the alloy are secured when the tin is between approximately 0.25 and 0.5%.

It has been found that, with the amounts of silicon and tin above specified, the maximum beneficial effect in respect to the increase in machinability imparted by a given amount of tellurium occurs when about 0.15% of this metal is present. This specific amount of the tellurium it has been found increases the machina'bility about 50%, but when the amount is increased to 0.7% the increase in machinability imparted by the tellurium is only about 66%. When the amount-of tellurium is increased to above about 1% no further material increase in machinability is observed. In general, with from 0.05 to 0.35% tellurium the greatest effects in increased machinability are secured in respect to the amount of tellurium present.

With amounts of tellurium above 0.5 to 0.7% segregation of the tellurium occurs to an excep- 40 tional degree, and commonly no assurance is had against segregation with any amount of tellurium over 0.35%., Segregation, causes planes of weakness in the alloy, resulting in cracking when the alloy is cold rolled or drawn, making it impossible to secure a satisfactory cold drawn or rolled product when material amounts of segregates are present.

It has further been found that the addition of tellurium up to 0.45% commonly increases the tensile strength of the alloy, but with higher amounts the tensile strength commonly markedly decreases. The addition of tellurium up to about 0.2% it has been found causes no decrease in the yield point of the alloy, and in many instances causes an increase, the yield point commonly gradually decreasing with the amounts of tellu- .rium above this value.. In general, the yield point may be considered as being increased to a maximum with about 0.15% tellurium. The hardness of the alloy it has been found increases to a maximum with the addition of tellurium up to about 0.2%, and decreases from this maximum when amounts higher than about 0.4% are added. In general, with the addition of amounts of tellurium above 0.5%, the hardness of the alloywill be decreased.

.of copper telluride (37% telluriumfwhichlg lias the beneficial effect of tellurium, are secured with about 0.15% of this metal.

In general, when the maximum eifects of tellurium are secured, the alloys may be cold drawn to secure, without heat treatment, a tensile strength of at least 100,000 pounds per square inch, with an elongation of at least about 13% in two inches, and a yield point (0.75%) of at least about 70,000 pounds per square inch. By heating the cold drawn rod to about 500 to 600 F. for 30 to minutes, and slowly cooling it by exposing it to air at room temperature, its yield point (0.75%) will be increased to at least 82,000

pounds per square inch without any substantial decrease in the tensile strength, hardness or elongation, and at the same time the alloys in the fully annealed, cold drawn and heat treated conditions are readily machinable. i h

The alloys may be prepared in the usualt' nian;

ner employed in an electric furnace, but a, loss of telluriumit is preferably addedi a melting point very much higher than that of tellurium.

.The alloy may contain small amounts of certain impuritifi,gorj pi. ;metals deliberately added to impart special characteristics or to change any of the above mentioned properties in respect to degree, so long as these impurities or metals do not adversely afiect in substance the mentioned properties. 'For example, the addition of small amounts of zinc up to less than 1 seems to have no deleterious efiect, and in fact somewhat improves the hot workability of the alloy. Likewise iron in amounts which do not exceed about 0.6% is not detrimental, and in efiect secures a beneficial increase in the hardness when the alloy is cold drawn or rolled from the fully annealed condition, and then heat treated to increase its yield point, this increase in hardness being noticeable when the amount of iron is as low as 0.1% of the alloy. Further, when iron is present zinc may be added up to about 2% without any detrimental effect on the properties of the alloy. Therefore, in the sense that the alloy may also contain impurities or small amounts of intentionally added metals not substantially destroying its characteristic properties, the balance of the alloy, in respect to the silicon, tin and tellurium, is substantially copper.

I claim:

7 1. Hot and cold workable, freely machinable, copper-base alloys of high tensile strength, yield point and ductility, capable when in the cold worked condition of being heat treated at temperatures below recrystallation temperatures to increase their yield point without substantial reduction in tensile strength and elongation, containing silicon, tin and tellurium within the following approximate ranges: 2.25 to 3.5% silicon, 0.25 to 2% tin, 0.05 to 0.5% tellurium, balance substantially copper, the maximum amount of tin for values of silicon between 2.25 and 3% varying between approximately 1.8 and 2% roughly directly and linearly with the amount of silicon and for values of silicon between 3 and 3.5% varying between approximately 1.7 and 2% roughlyinversely and linearly with the amount of silicon.

2. The alloys according to claim 1 in which the tellurium does not exceed 0.35%.

3. The alloys according to claim 1 in which the tellurium does not exceed 0.2%.

'4. The alloys according to claim proximately 0.15% tellurium.

RICHARD A. WILKINS.

1 having ap- 

